A Special Science Seminar for
Food writers, editors and Producers
From The American Chemical Society

Cocoa

Shirley O. CorriherAmerican Chemical SocietyNew York, October, 2007

Two Forms of Cocoa

Natural Cocoa

Cocoa is not fat free. The cocoa butter content runs from 10% to 35%. And, there can be major differences in flavors of different brands from the variety of tree, the fermentation, the roasting of the beans, and the fineness of grind of the powder. Cocoa beans are naturally tart and acidic. So, this powder, which is a very concentrated part of the cocoa bean, is acidic with a pH of about 5.5. Cocoa powder is a favorite of many pastry chefs because of its intense chocolate flavor.

You probably won’t find “natural cocoa” on the label. It is usually just labeled “cocoa” or “nonalkalized cocoa.”

Cocoa powder’s acidity is an advantage since it causes the proteins in baked goods to set rapidly.

Cocoa can be somewhat harsh. Alice Medrich points out that, unfortunately, with a few exceptions, the best cocoa beans are normally reserved for producing chocolate, not cocoa.

Dutch Process

Van Houten, who developed his process for making cocoa powder, also began treating the beans, nibs, liquor, or powder with an alkaline solution. This changes the color dramatically, changes the flavor, and produces a slight physical swelling of the cocoa particles, making them dissolve more easily. It also neutralizes free acids to give the cocoa powder a milder taste.

The color change is variable; it can go from a reddish-brown to a deep brown to almost black. If a baked product is very alkaline, it becomes very dark like Oreo cookies.

Dutch process cocoa is neutral or slightly alkaline, with a pH of about 7 or 8. The darker color, the milder flavor, and the lower acidity make Dutch process cocoa a favorite with many pastry makers. However, I also have seen many disasters caused by Dutch process cocoa. When a baked product is no longer acidic, it may not set. Cookies that are a big flat amoeba, and cakes that will not get done, are no fun. Unless I know that Dutch process cocoa will work in a recipe, I usually avoid it. It is not interchangeable with natural cocoa powder because of the problems its alkalinity can cause.

Working with Cocoa

Releasing Flavor

Many recipes using cocoa contain hot water or a hot liquid. More intense chocolate flavor can be obtained from cocoa by pouring a small amount of boiling liquid over the cocoa powder. This melts the cocoa butter and aids in dispersing cocoa particles.

Cocoa Acts Like Flour

When you are converting a plain cake recipe to a chocolate cake, if you use cocoa, you need to consider it as flour. You need to subtract the amount of cocoa that you have from the flour; otherwise the cake will have too much flour and be dry. Many recipes with cocoa make dry cakes just because the cook writing the recipe did not reduce the amount of flour to compensate for the cocoa. You can reduce the amount of flour in the recipe or add liquid to compensate for the additional starch.

Acidity Problems

Proteins (especially egg proteins) that set (cook) to hold baked goods together need a certain acidity to coagulate (cook). If the batter is not acidic enough, the cake or baked good will never set. You have pudding instead of cake. Because of its alkalinity, Dutch process cocoa can prevent the setting of baked goods.

I had a call from a chef in Los Angeles. She made biscotti every week for her restaurant. Someone had given her some very good Dutch process cocoa and she used it to make chocolate biscotti. She did not even look in the oven until it was time to remove the biscotti. To her shock, there were not her usual loaves that she would cut into slices and dry, but a big chocolate puddle! She had made this recipe for years--what on earth happened!

I explained that it was the Dutch process cocoa. Her batter was no longer acidic enough for the eggs (biscotti recipes have several eggs) to set, so she had a huge chocolate puddle.

Famous cookbook writer Susan Purdy called. She was working on her high-altitude baking book, Pie in the Sky, and at 9,000 feet all of her cakes worked except the chocolate. I asked if she was using Dutch process cocoa.She was stunned, “How did you know?”

At high altitudes, acidity is vital to set cakes quickly before they lose their leavening and fall. No Dutch process cocoa for cakes at high altitudes!

Dutch Process and Natural Cocoa Not Interchangeable

A recipe that works perfectly with natural cocoa may not work with Dutch process. The strong alkalinity of the Dutch process chocolate may reduce the acidity of the batter to the point that the proteins will no longer set and you may have soup.

Color Challenges

Alkalinity darkens the color of chocolate and can take it to black like Oreo cookies. There are Black Magic Cakes that contain as much as 2 teaspoons of baking soda just to make the batter so alkaline that the chocolate turns black.However adding that much leavening overleavens the cake causing it to sink in the center.

You can, so to speak, have your cake and eat it, too. Combine liquid from the recipe, the chocolate and the soda in a heavy sauce pan, heat with stirring until you see steam around the edge of the pot, turn off the heat and set aside while you make the cake (cream the butter and sugar, etc.). Allowing the chocolate and soda to stand together darkens the chocolate and the acidity of the chocolate causes the soda to react and release a lot of its carbon dioxide so that it will no longer overleaven.

Dishes with Cocoa Can Thin

Another starch-related problem is thinning. A dish containing cocoa and uncooked egg yolks (for example, chocolate mousse) can thin in the refrigerator overnight. An enzyme, alpha-amylase, in the egg yolks, destroys the starch gel formed by starch in the cocoa (which contributes to the thickening of the mousse), just as uncooked egg yolks thin starch custards. Heating after adding the egg yolks to inactivate the alpha-amylase will prevent this thinning.

Cocoa At A Glance

What to do?

Why?

Reduce the amount of flour by the amount of cocoa added.

Cocoa acts like flour in baking.

Recipes like chocolate mousse that contains raw egg yolks and cocoa need to be brought to a boil.

Alpha-amylase in raw egg yolks will destroy the starch gel and cause the mousse to thin upon standing.

The alkalinity of Dutch process cocoa can reduce the acidity of a batter to a point that the proteins will not set.

Use natural cocoa in recipes unless Dutch process is specified.

Pour boiling liquid over cocoa.

Boiling liquid aids in dissolving cocoa and releases more flavors from cocoa.

To make cocoa darker, use baking soda or Dutch process cocoa, or Dutch process cocoa and baking soda. When using soda, you need to let it stand with the cocoa in hot liquid to dissipate carbon dioxide to avoid over leavening.